[PATCH 1/1] mm: Better handling of adding new regions

[Zhang Boyang]

The code of dynamically adding new regions has two problems. First, it
always invalidate disk caches, which decreases performance severely.
Second, it request exactly "size" bytes for new region, ignoring region
overheads.

This patch makes adding new regions more priority than disk cache
invalidating. This patch also use "size + 1MB" as the size of new
region. This value can address the region overheads, and it can also
improve performance of small allocations when default heap is full.

Fixes: 887f98f0db43 (mm: Allow dynamically requesting additional memory regions)

Signed-off-by: Zhang Boyang <zhangboyang.id@gmail.com>
---
 grub-core/kern/mm.c | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/grub-core/kern/mm.c b/grub-core/kern/mm.c
index 75f6eacbe..e998454f8 100644
--- a/grub-core/kern/mm.c
+++ b/grub-core/kern/mm.c
@@ -410,6 +410,7 @@ grub_memalign (grub_size_t align, grub_size_t size)
 {
   grub_mm_region_t r;
   grub_size_t n = ((size + GRUB_MM_ALIGN - 1) >> GRUB_MM_ALIGN_LOG2) + 1;
+  grub_size_t rsize;
   int count = 0;
 
   if (!grub_mm_base)
@@ -423,6 +424,7 @@ grub_memalign (grub_size_t align, grub_size_t size)
      in name of sanity is beneficial. */
   if ((size + align) > ~(grub_size_t) 0x100000)
     goto fail;
+  rsize = size + 0x100000;
 
   align = (align >> GRUB_MM_ALIGN_LOG2);
   if (align == 0)
@@ -443,22 +445,16 @@ grub_memalign (grub_size_t align, grub_size_t size)
   switch (count)
     {
     case 0:
-      /* Invalidate disk caches.  */
-      grub_disk_cache_invalidate_all ();
-      count++;
-      goto again;
-
-    case 1:
       /* Request additional pages, contiguous */
       count++;
 
       if (grub_mm_add_region_fn != NULL &&
-          grub_mm_add_region_fn (size, GRUB_MM_ADD_REGION_CONSECUTIVE) == 
GRUB_ERR_NONE)
+          grub_mm_add_region_fn (rsize, GRUB_MM_ADD_REGION_CONSECUTIVE) == 
GRUB_ERR_NONE)
        goto again;
 
       /* fallthrough  */
 
-    case 2:
+    case 1:
       /* Request additional pages, anything at all */
       count++;
 
@@ -468,12 +464,18 @@ grub_memalign (grub_size_t align, grub_size_t size)
            * Try again even if this fails, in case it was able to partially
            * satisfy the request
            */
-          grub_mm_add_region_fn (size, GRUB_MM_ADD_REGION_NONE);
+          grub_mm_add_region_fn (rsize, GRUB_MM_ADD_REGION_NONE);
           goto again;
         }
 
       /* fallthrough */
 
+    case 2:
+      /* Invalidate disk caches.  */
+      grub_disk_cache_invalidate_all ();
+      count++;
+      goto again;
+
     default:
       break;
     }
-- 
2.30.2